This invention relates to an optical fiber end-surface polishing device which is adapted to polish the end surfaces of a large number of optical fibers with high polishing quality.
Optical connectors are being widely used as a means for connecting optical fibers for optical communication with each other.
An optical fiber to be connected by means of an optical connector is first attached to the central hole of a ferrule by adhesion or the like. Its end surface is then polished together with that of the ferrule until it becomes a flat specular surface. Any minute flaw left on the polished end surface of an optical fiber connector will lead to an increase in connection loss.
The connection end-surface of an optical fiber connector is polished at first by being rubbed against a polishing disc surface to which a polishing medium such as an abrasive film with a relatively large grain size is bonded. The polishing is further performed in several stages, replacing the abrasive film in each stage with a new one having a smaller grain size, until a specular surface is obtained.
There may be many factors which affect the polishing quality. Experiments which have been conducted by the inventor of the present invention and others suggest the direction in which the connection end-surface of an optical fiber connector is polished against the abrasive film surface strongly affects quality.
FIG. 1A is a schematic diagram showing a conventional polishing device in which a polishing disc 1 is turned on its own axis (this type of movement will be hereinafter referred to as "turning"), and in which an optical fiber connector 2 whose connection end-surface is to be polished is supported by a rotating arm 3.
In the example shown, the polishing disc 1, supporting a polishing medium, is turned around a center 0.
The optical fiber 2 whose connection end-surface is to be polished is attached to the tip end of the rotating arm 3, which makes a reciprocating movement in the direction indicated by the arrows.
Where this relative movement is utilized, the polishing is only effected in the turning direction of the polishing disc 1 and the rotating direction of the arm 3.
As a result, the polished surface is subject, as shown in FIG. 1B, to flaws owing to the turning of the polishing disc 1 and the reciprocating movement of the arm 3.
With a view to eliminating this problem, a polishing method was contrived in which, as shown in FIG. 2A, the connection 2 end-surface of an optical fiber connector is fixed at a point, with the polishing disc 1 being revolved around a point 0 with a turning radius R (this type of movement will be hereinafter referred to as "revolving"), thereby effecting polishing.
This method allows the connection end-surface of an optical fiber connector to be polished in all directions, as shown in FIG. 2B.
Accordingly, if the connection end-surface receives a flaw in one polishing direction, a subsequent polishing in another direction will efface it, thus making it possible to easily obtain a better polished surface than in the previously described example.
Apart from this, the inventor of the present invention filed a patent application titled "An Optical Fiber End-Surface Polishing Device" (Japanese patent application No. 62-135880). This application was also filed in the United States, claiming the Japanese priority (U.S. Ser. No. 07/172,322), and is now U.S. Pat. No. 4,831,784.
In the device according to these applications, the optical fiber end-surface is revolved while describing a relatively small circle, and the polishing disc is turned in a large circle.
As stated above, the rotating arm system shown in FIG. 1A is defective in polishing quality.
The device shown in FIG. 2A will yield better results than that of FIG. 1A. However, this system, in which the polishing plate 1 is revolved, is intended only for the polishing of the connection end-surface of a single optical fiber connector, so that it is not suited for mass production.
A more serious defect of this type of device is that, although its polishing disc is adapted to make a revolution, it is equipped with no mechanism for turning on its own axis. As a result, the connection end-surface of the optical fiber connector is moved only along the same polishing locus T, so that the abrasive film is soon worn out and pierced with holes, losing its polishing ability.
It is understood that the polishing of the connection end-surface of an optical fiber connector must always be performed with a new abrasive film surface. As stated above, a device in which the polishing disc only makes a revolution and is not turned on its own axis (FIGS. 2A and 2B) involves rapid deterioration of the abrasive film. Moreover, the system in which the connection end-surface to be polished moves repeatedly along the same locus on the abrasive film is disadvantageous not only in polishing quality but also in cost.
The optical fiber end-surface polishing device proposed by the inventor of the present invention operates in a more efficient and more stable manner than the above-described two conventional examples. However, the device is not without its problems. That is, since its polishing disc only turns around on its axis and the component supporting the optical fiber makes a movement corresponding to the revolution, the polishing quality fluctuates depending on the mounting position of the optical fiber.
That is, the polishing quality in some portions of an optical fiber end-surface is, in all probability, defective when compared to that in other portions thereof.
It is accordingly a principal object of this invention to provide an optical fiber end-surface polishing device in which the above-mentioned problems are eliminated with a simple mechanism.
A more specific object of this invention is to provide an optical fiber end-surface polishing device in which the mechanisms for revolution and turning are concentrated on the side of the polishing disc assembly, and in which mechanisms for correctly rubbing the optical fiber end-surface against the abrasive film surface are concentrated on the side where the optical fiber is supported, thereby making it possible to polish a large quantity of optical fibers with high quality.